AURORA, Colo. — An Aurora teenager accused of stabbing her mother 151 times and then beating her with a bat, pleaded not guilty by reason of insanity to the murder charge against her.

The teen’s defense attorney says 19-year-old Isabella Guzman is schizophrenic and the disorder led her to kill her mother in August 2013.

Guzman acted oddly during her first court appearance. A psychiatrist testified that she suffers from severe mental illness which her lawyer says prevents her from comprehending her role in causing her mother’s death.

The attorney indicated they were working on a plea deal which would likely send the teen to a state mental health institution indefinitely.